With the increasing development of display technologies, portable electronic devices such as smart phones and tablet computers are becoming more and more popular. In this case, people have more chances and time to use communication software, browse web pages or process emails in public. However, when in public places, such as on a public transport vehicle, if a portable electronic device is used, image information on the screen will probably be seen by a neighboring passenger. This easily causes leakage of private information of the user such as personal data or private passwords.
In traditional approaches, privacy glasses can be used in order to prevent other people from peeping. In this way, the user cannot clearly see images displayed on the portable electronic device until he/she wears the privacy glasses. Besides, a cover part arranged on the portable electronic device can be further used to cover circumferential regions of the display screen so as to narrow the view angle. However, both approaches need to additionally resort to auxiliary tools, which reduces the user's convenience in use.